A Pd / RE / CeSn catalyst, its preparation method and use

Abstract

The present invention provides a Pd / RE / CeSn catalyst, a preparation method thereof and uses thereof. The Pd / RE / CeSn catalyst comprises a cerium (Ce) tin (Sn) oxide solid solution as a carrier, and palladium (Pd) and a non-cerium rare earth metal RE supported on the carrier. The present invention uses a cerium tin oxide solid solution instead of traditional Al2O3, which has higher active lattice oxygen. Further, by using rare earth metal elements in the same group as Ce, it is beneficial for them to be doped into the lattice to form more oxygen vacancies. When used as a DOC catalyst, the obtained catalyst can effectively weaken the competitive reaction between CO and HC, and has strong low-temperature CO and HC co-oxidation performance, and can achieve complete conversion below 145 °C, so as to meet the requirements of low-temperature emissions. In the obtained catalyst, the addition amount of the rare earth metal is small, but the performance improvement effect is stable, which is beneficial to solving the cost and carrying out large-scale application.

Description

Technical Field

[0001] The present invention belongs to the field of catalysis, and relates to a Pd / RE / CeSn catalyst, a preparation method thereof and uses thereof. Background Art

[0002] In recent years, diesel vehicles have been developing rapidly. Diesel vehicles have superior environmental protection performance, good power performance and less fuel consumption compared with gasoline vehicles. Therefore, diesel vehicles have better economy compared with gasoline vehicles and are increasingly attracting attention and favor. At the same time, the exhaust emission standards of diesel vehicles are becoming increasingly strict, which also puts forward higher requirements for the after-treatment technology of diesel vehicle exhaust. A large amount of CO (carbon monoxide) and HC (hydrocarbons) will be contained in the exhaust of diesel vehicles. On the one hand, the generated CO and HC will cause harm to the environment, such as stratospheric ozone depletion, tropospheric ozone formation, photochemical smog, plant decay, etc. On the other hand, they can directly harm human health. Therefore, it is necessary to comprehensively treat CO and HC.

[0003] The catalytic oxidation technology can effectively achieve the simultaneous removal of HC and CO. An oxidation catalytic converter (DOC) is arranged in the engine exhaust pipe. Through the DOC catalyst therein, an oxidation reaction is realized to convert CO and HC in the engine exhaust into harmless water and carbon dioxide. It can be seen that the DOC catalyst is the core and key of the catalytic oxidation technology.

[0004] Considering that both CO and HC in the exhaust of diesel vehicles originate from regional stages such as uneven fuel mixing in the region and incomplete combustion caused by residual fuel on the cylinder surface, and belong to the main pollutants in the low-temperature emission range. Especially when the exhaust temperature is relatively low during cold start, the generation of pollutants is 1.05 - 2 times that of normal working conditions. Therefore, improving the co-oxidation activity of the DOC catalyst for HC and CO, especially the low-temperature activity, is the research focus in this catalytic field and is of great significance for the application and development of the DOC catalyst. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a Pd / RE / CeSn catalyst, a preparation method thereof and uses thereof. The Pd / RE / CeSn catalyst includes a cerium tin oxide solid solution as a carrier, and Pd and a non-cerium rare earth metal RE supported on the carrier. The present invention uses a cerium tin oxide solid solution instead of traditional Al 2 O 3, with higher active lattice oxygen, further utilizing rare earth metal elements in the same group as Ce, is conducive to their doping into the lattice to form more oxygen vacancies; when used as a DOC catalyst, the resulting catalyst can effectively weaken the competitive reaction between CO and HC, and has strong low-temperature CO and HC co-oxidation performance, thus meeting the requirements of low-temperature emissions.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a Pd / RE / CeSn catalyst, including a cerium tin oxide solid solution as a carrier, and Pd and a non-cerium rare earth metal RE supported on the carrier.

[0008] Pd / CeO 2 The catalyst is a commonly used material in the field of DOC catalysts, but to meet the requirements of simultaneously treating HC and CO at low temperatures, its activity needs to be further improved. For this reason, the present invention uses tin and a non-cerium rare earth metal for dual modification to form a cerium tin oxide solid solution to replace the traditional Al 2 O 3 As a carrier, it has higher active lattice oxygen, further utilizing rare earth metal elements in the same group as Ce, is conducive to their doping into the lattice of the carrier to form more oxygen vacancies; when used as a DOC catalyst, the resulting catalyst can effectively weaken the competitive reaction between CO and HC, and has strong low-temperature CO and HC co-oxidation performance, and can achieve complete conversion below 145 °C, thus meeting the requirements of low-temperature emissions. In the resulting catalyst, the addition amount of the rare earth metal is small, but the performance improvement effect is stable, which is conducive to solving the cost and large-scale application.

[0009] The following are the preferred technical solutions of the present invention, but not the limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical purpose and beneficial effects of the present invention can be better achieved and realized.

[0010] As a preferred technical solution of the present invention, the molar ratio of cerium to tin in the cerium tin oxide solid solution is (1-8):1, such as 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1 or 8:1, etc., but not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0011] Too large a cerium-tin molar ratio will cause the collapse of the solid solution structure, and it is easy to form independent oxides of tin and cerium rather than a solid solution. When the molar ratio is too small, it is easy to cause incomplete formation of the cerium tin solid solution.

[0012] Preferably, the loading amount of Pd is 0.8% to 1% of the mass of the cerium-tin oxide solid solution, such as 0.8%, 0.82%, 0.84%, 0.86%, 0.88%, 0.9%, 0.92%, 0.94%, 0.96%, 0.98% or 1%, etc., but not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0013] As the active center, if the loading amount of Pd is too small, the activity is poor. However, Pd is expensive, and when the loading amount is further increased, the improvement amplitude is small, and the cost performance is low.

[0014] Preferably, the non-cerium rare earth metal RE includes at least one of Y, Pr or La. For example, it can be a combination of Y and Pr, a combination of Y and La, or a combination of Pr and La, and preferably Y.

[0015] Preferably, the loading amount of the non-cerium rare earth metal RE is 0.5% to 15% of the mass of the cerium-tin oxide solid solution, such as 0.5%, 1%, 1.5%, 2%, 3.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5% or 15%, etc., preferably 4% to 10%, but not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0016] If the loading amount of RE is too low, the best activity cannot be achieved. If the loading amount of RE is too high, the original cerium-tin solid solution will be covered, and the noble metal will be directly loaded on RE rather than the solid solution, resulting in activity loss.

[0017] In a second aspect, the present invention provides a preparation method of the Pd / RE / CeSn catalyst described in the first aspect. The preparation method includes:

[0018] Mix a Ce source, a Sn source and a precipitant, carry out a precipitation reaction to obtain a precipitate, and perform a first calcination on the obtained precipitate to obtain a cerium-tin oxide solid solution;

[0019] Mix the obtained cerium-tin oxide solid solution with an RE source, and perform a second calcination to obtain an RE / CeSn intermediate;

[0020] Mix the obtained intermediate with a Pd source, and perform a third calcination to obtain a Pd / CeSn catalyst.

[0021] The present invention synthesizes a cerium-tin solid solution material by a coprecipitation method, and uses it as a carrier to respectively load a certain amount of non-cerium rare earth metal and noble metal through two impregnations, thereby preparing a CO and HC co-oxidation catalyst.

[0022] As a preferred technical solution of the present invention, the Ce source, Sn source, RE source and Pd source are all water-soluble, and the mixing is carried out in an aqueous solution system.

[0023] Preferably, the preparation method includes preparing solution A by mixing the Ce source and the Sn source, preparing solution B with a precipitating agent, and adding solution A dropwise to solution B for mixing.

[0024] It should be noted that when dropping solution B into solution A, it is easy to cause uneven precipitation due to too high local concentration.

[0025] Preferably, the precipitating agent includes ammonia water.

[0026] Preferably, the precipitating agent further includes hydrogen peroxide.

[0027] Hydrogen peroxide is mainly used to adjust the valence states of cerium and tin, making it easier for the two to form a solid solution.

[0028] Preferably, solution B is composed of water, hydrogen peroxide and ammonia water with a volume ratio of (3-4):(1-1.2):(3-4), such as 3:1:3, 3.6:1:3, 4:1:3, 3:1.1:3, 3.6:1.1:3, 3.8:1.1:3, 3:1.2:3, 3.3:1.2:3, 3.6:1.2:3, 3.8:1.2:3, 3:1:3.4, 3.3:1:3.4, 3.6:1:3.4, 3.8:1:3.4, 4:1:3.4, 3:1.1:3.4, 3.3:1.1:3.4, 3.8:1.1:3.4, 4:1.1:3.4, 3:1.2:3.4, 3.6:1.2:3.4, 3.8:1.2:3.4, 4:1.2:3.4, 3:1:4, 3.3:1:4, 3.6:1:4, 3.8:1:4, 4:1:4, 3:1.1:4, 3.8:1.1:4, 3.3:1.2:3.4, 3.6:1.2:4, 3.8:1.2:4 or 4:1.2:4, etc., but not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0029] As a preferred technical solution of the present invention, the temperature of the first roasting is 500-1000 °C, such as 500 °C, 550 °C, 600 °C, 650 °C, 700 °C, 750 °C, 800 °C, 850 °C, 900 °C, 950 °C or 1000 °C, etc., but not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0030] Preferably, the time of the first roasting is 2 to 4 h, such as 2 h, 2.4 h, 2.8 h, 3.2 h, 3.6 h or 4 h, etc., but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0031] As a preferred technical solution of the present invention, after the cerium tin oxide solid solution is mixed with the RE source, it is first dried to obtain a first dried body, and the obtained first dried body is subjected to a second roasting.

[0032] Preferably, after the intermediate is mixed with the Pd source, it is first dried to obtain a second dried body, and the obtained second dried body is subjected to a third roasting.

[0033] Preferably, the drying method includes first rotary evaporation under reduced pressure and then drying at 100 - 120 °C, such as 100 °C, 104 °C, 108 °C, 112 °C, 116 °C or 120 °C, etc., but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0034] As a preferred technical solution of the present invention, the temperature of the second roasting is 450 - 550 °C, such as 450 °C, 460 °C, 470 °C, 480 °C, 490 °C, 500 °C, 510 °C, 520 °C, 530 °C, 540 °C or 550 °C, etc., and the time is 2 - 4 h, such as 2 h, 2.4 h, 2.8 h, 3.2 h, 3.6 h or 4 h, etc., but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0035] Preferably, the temperature of the third roasting is 450 - 550 °C, such as 450 °C, 460 °C, 470 °C, 480 °C, 490 °C, 500 °C, 510 °C, 520 °C, 530 °C, 540 °C or 550 °C, etc., and the time is 2 - 4 h, such as 2 h, 2.4 h, 2.8 h, 3.2 h, 3.6 h or 4 h, etc., but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0036] As a preferred technical solution of the present invention, the Ce source includes cerium nitrate, the Sn source includes tin tetrachloride, the Pd source includes palladium nitrate, and the RE source includes nitrates of corresponding rare earth metals, such as yttrium nitrate.

[0037] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0038] Using Ce(NO 3 ) 3 ·6H 2 O as the Ce source, SnCl 4 ·5H 2O serves as the Sn source, NH 3 ·H 2 O and H 2 O 2 serves as the precipitant; according to the molar ratio of cerium to tin being (1 - 8):1, the Ce source and the Sn source are formulated into solution A; according to the volume ratio of deionized water, hydrogen peroxide, and ammonia water being (3 - 4):(1 - 1.2):(3 - 4), solution B is formulated;

[0039] Solution A is added dropwise to solution B for precipitation reaction while performing magnetic stirring; after solution A is completely added to solution B, the obtained precipitate is subjected to ultrasonic treatment for 10 - 40 min, and then uniformly stirred for 0.5 - 2 h; after the ultrasonic and stirred solution system is left standing for a period of time, the supernatant is removed to obtain a precipitate, and the precipitate is filtered and washed until neutral; the precipitate is placed in an oven at 100 - 120 °C for drying, and then placed in a muffle furnace for the first calcination at 500 - 1100 °C for 2 - 4 h to obtain a cerium tin oxide solid solution;

[0040] Using Y(NO 3 ) 3 ·6H 2 O as the RE source, it is formulated into solution C; according to the loading amount of Y being 0.5% - 15% of the mass of the cerium tin oxide solid solution, the obtained cerium tin oxide solid solution is put into solution C, subjected to ultrasonic treatment for 10 - 40 min, and then stirred for 0.5 - 2 h, followed by reduced pressure rotary evaporation. After the water is evaporated to dryness, it is placed in an oven at 100 - 120 °C for drying to obtain a first dried body, and the obtained first dried body is placed in a muffle furnace for the second calcination at 450 - 550 °C for 2 - 4 h to obtain a Y / CeSn intermediate;

[0041] Using Pd(NO 3 ) 2 ·2H 2 O as the Pd source, it is formulated into solution D; according to the loading amount of Pd being 0.8% - 1% of the mass of the cerium tin oxide solid solution, the obtained intermediate is put into solution D, subjected to ultrasonic treatment for 10 - 40 min, and then stirred for 0.5 - 2 h, followed by reduced pressure rotary evaporation. After the water is evaporated to dryness, it is placed in an oven at 100 - 120 °C for drying to obtain a second dried body, and the obtained second dried body is placed in a muffle furnace for the third calcination at 450 - 550 °C for 2 - 4 h to obtain a Pd / CeSn catalyst.

[0042] In a third aspect, the present invention provides a use of the Pd / RE / CeSn catalyst described in the first aspect, and the use includes being used for the co - oxidation of HC and CO.

[0043] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0044] The present invention uses double modification with tin and non-cerium rare earth metals to form a CeSn catalyst as the carrier instead of the traditional Al 2 O 3 catalyst. The rare earth elements in the same group as cerium are beneficial to their doping into the lattice of the carrier to form more oxygen vacancies, effectively weakening the competitive reaction between CO and HC; the obtained Pd / RE / CeSn catalyst, especially the Pd / Y / CeSn catalyst, has excellent low-temperature HC and CO co-oxidation performance and can be completely converted below 145 °C, thus meeting the low-temperature emission requirements; the addition amount of RE metal in the obtained catalyst is small, the cost increase is small, but the improvement effect on the activity is stable, which is beneficial to large-scale application. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a graph of the catalytic oxidation results of CO by the catalysts obtained in Examples 1-5 and Comparative Examples 3-4 at different temperatures;

[0046] Figure 2 It is a graph of the catalytic oxidation results of C 3 H 6 by the catalysts obtained in Examples 1-5 and Comparative Examples 3-4 at different temperatures;

[0047] Figure 3 It is a graph of the catalytic oxidation results of CO in the 3-cycle test of the catalyst obtained in Example 1;

[0048] Figure 4 It is a graph of the catalytic oxidation results of C 3 H 6 in the 3-cycle test of the catalyst obtained in Example 1;

[0049] Figure 5 It is a graph of the life test results of the catalyst obtained in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0050] The technical solution of the present invention will be further described below through specific embodiments.

[0051] Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0052] Example 1

[0053] This example provides a Pd / RE / CeSn catalyst. The preparation method of the Pd / RE / CeSn catalyst includes:

[0054] Using Ce(NO 3 ) 3 ·6H2 O is used as the Ce source, and SnCl 4 ·5H 2 O is used as the Sn source, and NH 3 ·H 2 O and H 2 O 2 is used as the precipitant; according to the molar ratio of cerium to tin being 4:1, 24 g of the Ce source and 6 g of the Sn source are dissolved in 60 mL of deionized water to prepare solution A; according to the volume ratio of deionized water, hydrogen peroxide and ammonia water being 3.5:1.1:3.5, solution B is prepared;

[0055] Solution A is added dropwise to solution B for precipitation reaction while magnetic stirring is carried out; after solution A is completely added to solution B, the obtained precipitate is ultrasonically treated for 30 min and then uniformly stirred for 1 h; after the ultrasonically treated and stirred solution system is left standing for a period of time, the supernatant is removed to obtain a precipitate, and the precipitate is suction filtered and washed until neutral; the precipitate is placed in an oven at 110 °C for drying and then placed in a muffle furnace for the first calcination at 500 °C for 3 h to obtain a cerium-tin oxide solid solution as the carrier, denoted as CeSn;

[0056] Using Y(NO 3 ) 3 ·6H 2 O as the RE source, solution C is prepared; according to the loading amount of Y being 5% of the mass of the cerium-tin oxide solid solution, the obtained cerium-tin oxide solid solution is put into solution C, ultrasonically treated for 30 min, then stirred for 1 h, and then subjected to reduced-pressure rotary evaporation. After the water is evaporated to dryness, it is placed in an oven at 110 °C for drying to obtain the first dried body. The obtained first dried body is placed in a muffle furnace for the second calcination at 550 °C for 3 h to obtain an intermediate, denoted as 5Y / CeSn;

[0057] Using Pd(NO 3 ) 2 ·2H 2 O as the Pd source, solution D is prepared; according to the loading amount of Pd being 0.9% of the mass of the cerium-tin oxide solid solution, the obtained intermediate is put into solution D, ultrasonically treated for 30 min, then stirred for 1 h, and then subjected to reduced-pressure rotary evaporation. After the water is evaporated to dryness, it is placed in an oven at 110 °C for drying to obtain the second dried body. The obtained second dried body is placed in a muffle furnace for the third calcination at 500 °C for 3 h to obtain the Pd / RE / CeSn catalyst, denoted as Pd / 5Y / CeSn.

[0058] Example 2

[0059] This example provides a Pd / RE / CeSn catalyst and a preparation method thereof. In this preparation method, the loading amount of Y is adjusted from 5% of the mass of the cerium tin oxide solid solution to 0.5%. The obtained intermediate is denoted as 0.5Y / CeSn, and the obtained catalyst is denoted as Pd / 0.5Y / CeSn. Except for the above, other conditions are exactly the same as those in Example 1.

[0060] Example 3

[0061] This example provides a Pd / RE / CeSn catalyst and a preparation method thereof. In this preparation method, the loading amount of Y is adjusted from 5% of the mass of the cerium tin oxide solid solution to 2.5%. The obtained intermediate is denoted as 2.5Y / CeSn, and the obtained catalyst is denoted as Pd / 2.5Y / CeSn. Except for the above, other conditions are exactly the same as those in Example 1.

[0062] Example 4

[0063] This example provides a Pd / RE / CeSn catalyst and a preparation method thereof. In this preparation method, the loading amount of Y is adjusted from 5% of the mass of the cerium tin oxide solid solution to 7.5%. The obtained intermediate is denoted as 7.5Y / CeSn, and the obtained catalyst is denoted as Pd / 7.5Y / CeSn. Except for the above, other conditions are exactly the same as those in Example 1.

[0064] Example 5

[0065] This example provides a Pd / RE / CeSn catalyst and a preparation method thereof. In this preparation method, the loading amount of Y is adjusted from 5% of the mass of the cerium tin oxide solid solution to 15%. The obtained intermediate is denoted as 15Y / CeSn, and the obtained catalyst is denoted as Pd / 15Y / CeSn. Except for the above, other conditions are exactly the same as those in Example 1.

[0066] Example 6

[0067] This example provides a Pd / RE / CeSn catalyst and a preparation method thereof. In this preparation method, the cerium tin molar ratio is adjusted from 4:1 to 0.5:1. The obtained cerium tin oxide solid solution is denoted as 0.5-CeSn, the obtained intermediate is denoted as 5Y / 0.5-CeSn, and the obtained catalyst is denoted as Pd / 5Y / 0.5-CeSn. Except for the above, other conditions are exactly the same as those in Example 1.

[0068] Example 7

[0069] This example provides a Pd / RE / CeSn catalyst. In the preparation method of the Pd / RE / CeSn catalyst, the cerium-tin molar ratio is adjusted from 4:1 to 1:1. The obtained cerium-tin oxide solid solution is denoted as 1-CeSn, the obtained intermediate is denoted as 5Y / 1-CeSn, and the obtained catalyst is denoted as Pd / 5Y / 1-CeSn. Except for the above, other conditions are exactly the same as those in Example 1.

[0070] Example 8

[0071] This example provides a Pd / RE / CeSn catalyst. In the preparation method of the Pd / RE / CeSn catalyst, the cerium-tin molar ratio is adjusted from 4:1 to 8:1. The obtained cerium-tin oxide solid solution is denoted as 8-CeSn, the obtained intermediate is denoted as 5Y / 8-CeSn, and the obtained catalyst is denoted as Pd / 5Y / 8-CeSn. Except for the above, other conditions are exactly the same as those in Example 1.

[0072] Example 9

[0073] This example provides a Pd / RE / CeSn catalyst. In the preparation method of the Pd / RE / CeSn catalyst, the cerium-tin molar ratio is adjusted from 4:1 to 9:1. The obtained cerium-tin oxide solid solution is denoted as 9-CeSn, the obtained intermediate is denoted as 5Y / 9-CeSn, and the obtained catalyst is denoted as Pd / 5Y / 9-CeSn. Except for the above, other conditions are exactly the same as those in Example 1.

[0074] Example 10

[0075] This example provides a catalyst. The preparation method of the catalyst includes:

[0076] Using Ce(NO 3 ) 3 ·6H 2 O as the Ce source, SnCl 4 ·5H 2 O as the Sn source, NH 3 ·H 2 O and H 2 O 2 As the precipitants; according to the cerium-tin molar ratio of 4:1, 24 g of the Ce source and 6 g of the Sn source are dissolved in 60 mL of deionized water to prepare solution A; solution B is prepared according to the volume ratio of deionized water, hydrogen peroxide and ammonia of 3.5:1.1:3.5;

[0077] Add solution A dropwise to solution B to carry out a precipitation reaction while performing magnetic stirring; after solution A is completely added to solution B, ultrasonically treat the obtained precipitate for 30 min, and then perform uniform stirring for 1 h; after standing the ultrasonically treated and stirred solution system for a period of time, remove the supernatant to obtain a precipitate, and perform suction filtration and washing of the precipitate until it is neutral; place the precipitate in an oven at 110 °C to dry, and then place it in a muffle furnace for the first calcination at 500 °C for 3 h to obtain a cerium tin oxide solid solution as a support, denoted as CeSn;

[0078] Using Y(NO 3 ) 3 ·6H 2 O as the RE source and Pd(NO 3 ) 2 ·2H 2 O as the Pd source, prepare solution E; according to the loading amount of Y being 5% of the mass of the cerium tin oxide solid solution and the loading amount of Pd being 0.9% of the mass of the cerium tin oxide solid solution, control the dosages of the RE source and the Pd source and put the obtained cerium tin oxide solid solution into solution E, perform ultrasonic treatment for 30 min, then perform stirring for 1 h, and then perform rotary evaporation under reduced pressure. After evaporating the water, place it in an oven at 110 °C to dry to obtain a first dried body, and place the obtained first dried body in a muffle furnace for the second calcination at 550 °C for 3 h to obtain a catalyst, denoted as Pd+5Y / CeSn.

[0079] Example 11

[0080] This example provides a Pd / RE / CeSn catalyst. The preparation method of the Pd / RE / CeSn catalyst adjusts the RE source from Y(NO 3 ) 3 ·6H 2 O to an equimolar amount of Pr(NO 3 ) 3 ·6H 2 O, denote the obtained intermediate as 5Pr / CeSn, and denote the obtained catalyst as Pd / 5Pr / CeSn. Except for the above, other conditions are exactly the same as those in Example 1.

[0081] Example 12

[0082] This example provides a Pd / RE / CeSn catalyst. The preparation method of the Pd / RE / CeSn catalyst adjusts the RE source from Y(NO 3 ) 3 ·6H 2 O to an equimolar amount of La(NO 3 ) 3 ·6H 2O, the obtained intermediate is denoted as 5La / CeSn, and the obtained catalyst is denoted as Pd / 5La / CeSn. Except for the above, other conditions are exactly the same as those in Example 1.

[0083] Comparative Example 1

[0084] This comparative example provides a catalyst. In the preparation method of the catalyst, no Ce source is used, and the Ce source is replaced with an equimolar amount of Sn source. The obtained support is denoted as Sn-0, the obtained intermediate is denoted as 5Y / Sn-0, and the obtained catalyst is denoted as Pd / 5Y / Sn-0. Except for the above, other conditions are exactly the same as those in Example 1.

[0085] Comparative Example 2

[0086] This comparative example provides a catalyst. In the preparation method of the catalyst, no Sn source is used, and the Sn source is replaced with an equimolar amount of Ce source. The obtained support is denoted as Ce-0, the obtained intermediate is denoted as 5Y / Ce-0, and the obtained catalyst is denoted as Pd / 5Y / Ce-0. Except for the above, other conditions are exactly the same as those in Example 1.

[0087] Comparative Example 3

[0088] This comparative example provides a catalyst. In the preparation method of the catalyst, no RE source is used, and the obtained support is directly put into Solution D. The obtained catalyst is denoted as Pd / CeSn. Except for the above, other conditions are exactly the same as those in Example 4.

[0089] Comparative Example 4

[0090] This comparative example provides a catalyst. The preparation method of the catalyst includes:

[0091] Using Y(NO 3 ) 3 ·6H 2 O as the RE source, grinding it and then drying it in an oven at 110°C, and then roasting it in a muffle furnace at 550°C for 3 h to obtain a support, denoted as Y 2 O 3 ;

[0092] Using Pd(NO 3 ) 2 ·2H 2 O as the Pd source, preparing it into Solution D; according to the Pd loading amount being 0.9% of the mass of the support, putting the obtained support into Solution D, performing ultrasonic treatment for 30 min, then stirring for 1 h, followed by rotary evaporation under reduced pressure to evaporate the water, drying it in an oven at 110°C, and then roasting it in a muffle furnace at 500°C for 3 h to obtain a catalyst, denoted as Pd / Y 2 O 3 .

[0093] Catalyst performance test:

[0094] Take the catalysts obtained in the examples and comparative examples, 40 - 60 mesh, and put them into the catalyst activity evaluation device. The activity evaluation is carried out in a fixed-bed reactor. The test conditions are: CO = 4000 ppm, C 3 H 6 = 1000 ppm, O 2 = 10%; the total flow rate is 300 mL / min, and the reaction space velocity is about 240000 ml / g·h -1 . The test results are recorded in Table 1.

[0095] Table 1

[0096]

[0097]

[0098] Note: In Table 1, T 5 represents the temperature corresponding to a 50% conversion rate; 1st represents the first catalytic oxidation of the catalyst, and 2nd and 3rd represent the second and third catalytic oxidations during the cyclic testing of the catalyst.

[0099] Figure 1 and Figure 2 are the catalytic oxidation results of the catalysts obtained in Examples 1 - 5 and Comparative Examples 3 - 4 for CO and C 3 H 6 . It can be seen from Table 1 that the optimal loading amount of Y is 5%. When it is less than 5%, the activity can continue to increase. When it exceeds 5%, further increasing the loading amount will lead to a decrease in activity, and when it exceeds 15%, the activity will even be inhibited;

[0100] Figure 3 and Figure 4 are the catalytic oxidation results of the catalyst obtained in Example 1 for 3 cyclic tests. It can be seen from Table 1 that the catalyst has good cyclic stability and can be used repeatedly for many times;

[0101] Figure 5 are the results of the life test of the catalyst obtained in Example 1. It can be seen from the figure that the catalyst can continuously work for more than 3000 min without a significant decrease in activity, and has significant durability.

[0102] By comparing Example 1 with Examples 6 - 9, it can be found that although these catalysts all have good stability, when the tin ratio is small, the incomplete formation of the solid solution leads to the activity not reaching the optimum, and when the tin ratio is large, the presence of non-solid solution tin causes a decrease in activity.

[0103] As can be seen from Example 1 and Example 10, Y and Pd must be impregnated step by step. Simultaneous impregnation will cause the two elements to shield each other's sites, reducing the activity.

[0104] As can be seen from Comparative Examples 11 to 12, the rare earth element Y shows better compatibility with the solid solution than Pr and La, and the light-off temperature is reduced by 20 °C.

[0105] As can be seen from Comparative Example 1, Comparative Example 1 and Comparative Example 2, Y has the best catalytic activity in the cerium-tin solid solution, and the light-off temperature is reduced by more than 70 °C compared with the single oxide.

[0106] The present invention uses the above embodiments to illustrate the detailed structural features of the present invention. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent replacement of the components selected by the present invention, and the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

[0107] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0108] In addition, it should be noted that, in the above specific embodiments, the various specific technical features described can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0109] In addition, any combination can be made between various different embodiments of the present invention as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A Pd / RE / CeSn catalyst for the co-oxidation of HC and CO, characterized in that, it comprises a cerium tin oxide solid solution as a carrier, and Pd and a non-cerium rare earth metal RE supported on the carrier; the loading amount of the non-cerium rare earth metal RE is 4% - 7.5% of the mass of the cerium tin oxide solid solution; the Pd / RE / CeSn catalyst is prepared by the following method, and the preparation method consists of the following steps: Mix a Ce source, a Sn source and a precipitant, carry out a precipitation reaction to obtain a precipitate, and perform a first calcination on the obtained precipitate to obtain a cerium tin oxide solid solution; Mix the obtained cerium tin oxide solid solution with an RE source, and perform a second calcination to obtain an RE / CeSn intermediate; Mix the obtained intermediate with a Pd source, and perform a third calcination to obtain a Pd / RE / CeSn catalyst.

2. The Pd / RE / CeSn catalyst according to claim 1, characterized in that, the molar ratio of cerium to tin in the cerium tin oxide solid solution is (1 - 8):

1.

3. The Pd / RE / CeSn catalyst according to claim 1, characterized in that, the loading amount of Pd is 0.8% - 1% of the mass of the cerium tin oxide solid solution.

4. The Pd / RE / CeSn catalyst according to claim 1, characterized in that, the non-cerium rare earth metal RE includes at least one of yttrium, praseodymium or lanthanum.

5. The Pd / RE / CeSn catalyst according to claim 4, characterized in that, the non-cerium rare earth metal RE is yttrium.

6. A preparation method of the Pd / RE / CeSn catalyst according to any one of claims 1 - 5, characterized in that, the preparation method consists of the following steps: Mix a Ce source, a Sn source and a precipitant, carry out a precipitation reaction to obtain a precipitate, and perform a first calcination on the obtained precipitate to obtain a cerium tin oxide solid solution; Mix the obtained cerium tin oxide solid solution with an RE source, and perform a second calcination to obtain an RE / CeSn intermediate; Mix the obtained intermediate with a Pd source, and perform a third calcination to obtain a Pd / RE / CeSn catalyst.

7. The preparation method according to claim 6, characterized in that, the Ce source, the Sn source, the RE source and the Pd source are all water-soluble, and the mixing is carried out in an aqueous solution system.

8. The preparation method according to claim 6, characterized in that, the preparation method includes preparing a solution A from a Ce source and a Sn source, preparing a solution B from a precipitant, and dropping solution A into solution B for mixing.

9. The preparation method according to claim 8, characterized in that, the precipitant includes ammonia water.

10. The preparation method according to claim 9, characterized in that, the precipitant further includes hydrogen peroxide.

11. The preparation method according to claim 10, characterized in that, solution B consists of water, hydrogen peroxide and ammonia water with a volume ratio of (3 - 4):(1 - 1.2):(3 - 4).

12. The preparation method according to claim 6, characterized in that, the temperature of the first calcination is 500 - 1000 °C.

13. The preparation method according to claim 6, characterized in that, the time of the first calcination is 2 to 4 h.

14. The preparation method according to claim 6, characterized in that, after the cerium tin oxide solid solution is mixed with the RE source, it is first dried to obtain a first dried body, and the obtained first dried body is subjected to a second calcination.

15. The preparation method according to claim 6, characterized in that, after the intermediate is mixed with the Pd source, it is first dried to obtain a second dried body, and the obtained second dried body is subjected to a third calcination.

16. The preparation method according to claim 14, characterized in that, the drying method includes first rotary evaporation under reduced pressure and then drying at 100 to 120 °C.

17. The preparation method according to claim 6, characterized in that, the temperature of the second calcination is 450 to 550 °C and the time is 2 to 4 h.

18. The preparation method according to claim 6, characterized in that, the temperature of the third calcination is 450 to 550 °C and the time is 2 to 4 h.

19. The preparation method according to claim 6, characterized in that, the Ce source includes cerium nitrate, the Sn source includes tin tetrachloride, the Pd source includes palladium nitrate, and the RE source includes nitrates of corresponding rare earth metals.

20. The preparation method according to claim 6, characterized in that, the preparation method includes the following steps: Using Ce(NO 3 ) 3 ·6H 2 O as the Ce source, SnCl 4 ·5H 2 O as the Sn source, NH 3 ·H 2 O and H 2 O 2 as the precipitants; preparing solution A by mixing the Ce source and the Sn source according to a cerium-tin molar ratio of (1-8):1; preparing solution B according to a volume ratio of deionized water, hydrogen peroxide, and ammonia water of (3-4):(1-1.2):(3-4). Dropwise add solution A into solution B for precipitation reaction while performing magnetic stirring; After solution A is completely added to solution B, the obtained precipitate is ultrasonically treated for 10 to 40 min, and then uniformly stirred for 0.5 to 2 h; after the ultrasonically treated and stirred solution system is left standing for a period of time, the supernatant is removed to obtain a precipitate, and the precipitate is suction filtered and washed to neutral; the precipitate is placed in an oven at 100 to 120 °C for drying, and then placed in a muffle furnace for the first calcination at 500 to 1100 °C for 2 to 4 h to obtain a cerium tin oxide solid solution; Using Y(NO 3 ) 3 ·6H 2 O as the RE source, it is formulated into solution C; according to the loading amount of Y being 4% - 7.5% of the mass of the cerium tin oxide solid solution, the obtained cerium tin oxide solid solution is put into solution C, ultrasonic treatment is carried out for 10 - 40 min, then stirring is carried out for 0.5 - 2 h, followed by reduced-pressure rotary evaporation. After the water is evaporated to dryness, it is placed in an oven at 100 - 120 °C for drying to obtain the first dried body. The obtained first dried body is placed in a muffle furnace and subjected to a second calcination at 450 - 550 °C for 2 - 4 h to obtain the Y / CeSn intermediate; Using Pd(NO 3 ) 2 ·2H 2 O as the Pd source, it was formulated into solution D; according to the Pd loading amount being 0.8% - 1% of the mass of the cerium tin oxide solid solution, the obtained intermediate was put into solution D, ultrasonic treatment was carried out for 10 - 40 min, then stirring was carried out for 0.5 - 2 h, followed by rotary evaporation under reduced pressure. After the water was evaporated to dryness, it was placed in an oven at 100 - 120 °C for drying to obtain a second dried body. The obtained second dried body was placed in a muffle furnace and calcined at 450 - 550 °C for 2 - 4 h to obtain the Pd / CeSn catalyst.

21. The use of the Pd / RE / CeSn catalyst according to any one of claims 1-5, characterized in that, the use includes being used for the co-oxidation of HC and CO.

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